The RSA encryption algorithm is a public-key cryptosystem proposed by Rivest, Shamir, and Adleman. RSA is named from the initial letters of the surnames of Rivest, Shamir, and Adleman. It is considered to be theoretically the most mature and perfect cryptosystem so far. The RSA encryption algorithm is an asymmetric cryptographic algorithm. That is, the algorithm needs a pair of keys, namely, a public key (n, e) and a private key (n, d), where the public key (n, e) is used for encryption, and the private key (n, d) is used for decryption. The algorithm is as follows: setting A as a plaintext, and B as a ciphertext, the encryption equation is “B=Ae mod n”, and the decryption equation is “A=Bd mod n”, where “mod” represents a modular operation, that is, taking the remainder after dividing one integer by another integer, without considering the quotient. As an example, 7 mod 3=1: for 7 divided by 3, the quotient is 2 and the remainder is 1, and the remainder 1 is the result of the mod operation.
During RSA decryption, it is needed to obtain the ciphertext B and the private key (n, d), and perform a modular exponentiation operation by using A=Bd mod n to obtain the plaintext A. However, the existing decryption method generally uses a general-purpose processor, such as a CPU, to perform RSA decryption, but one CPU core can only perform one RSA decryption operation task at a time. Thus, the RSA decryption efficiency is low.